Delusional rockstar engineers might really have this kind of opinion of their LLMs and their colleagues.
With less sarcasm, how bad is Microsoft as a workplace? The source of this kind of naively arrogant proclamation can be anything from a single rotten apple, to a critical mass of unchecked idiots in the same business unit, to normal for the company culture, to a top-down mandate.
Maybe the plan is not testing because they think that Rust is "safe" and automatic translation is smarter than a typical Microsoft employee.